1. Field of the Invention
The present invention is in the field of hoppers for use with solid particulate materials, such as grain. More specifically, there is described a hopper that is a combination of a conical hopper and a one-dimensional hopper. The combination hopper prevents rat-holing of the material and bin hangups, while conserving on the vertical headroom required to accommodate the combination hopper.
2. The Prior Art
In U.S. Pat. No. 4,958,741 issued Sep. 25, 1990 to the present inventor, there is described a bin module that includes a first section that diverges upwardly from a circular outlet to an oval-shaped upper edge. In the invention of U.S. Pat. No. 4,958,741, this first section is joined end-to-end to a second section that provides a transition from an oval to a circular shape. This arrangement differs from the arrangements described herein in two significant ways.
First, in U.S. Pat. No. 4,958,741 the sections are joined end-to-end. In contrast, in the present invention, the sections are physically integrated, resulting in reduced height.
Second, in U.S. Pat. No. 4,958,741 the upper section has a specific shape, which is different from the shapes used in the present invention for the upper section. In this way, the present invention is seen to extend the earlier work to new ground; i.e., to shapes that were previously thought to be intractable.
Several considerations drive the design of hoppers. First, it is important that the material not form a bridge or arch within the hopper, because such an arch interferes or terminates the flow of material from the bottom of the hopper. If and when the arch collapses, the material may surge from the hopper. It is well known that arching can be eliminated if the opening at the bottom of the hopper is large enough.
A second consideration in the design of hoppers is that the wall of the hopper must be steep enough so that the material will slide smoothly along the wall during discharge. If the wall is not steep enough, a thick layer of material will cling to the wall and discharge will take place from only a limited region near the axis of the hopper, a condition referred to as "rat-holing." For a hopper having the shape of a section of a right circular cone, the largest semi-apex angle at which mass flow will occur, for a particular material is known as the mass flow angle for that particular material.
The present invention is responsive to both of these considerations and results in a combined hopper that eliminates both arching and rat-holing.